Hypokalemia laboratory findings: Difference between revisions
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Many labs can be helpful. The transtubular potasium gradient (TTKG), urine potassium and urine chloride levels can help define the etiology of hypokalemia. | Many labs can be helpful. The transtubular potasium gradient (TTKG), urine potassium and urine chloride levels can help define the etiology of hypokalemia. | ||
== Laboratory Findings == | == Laboratory Findings == | ||
* Complete blood count (CBC) | * [[Complete blood count]] (CBC) | ||
* Blood urea nitrogen (BUN)/creatinine | * [[Blood urea nitrogen]] (BUN)/[[creatinine]] | ||
* Calcium | * [[Calcium]] | ||
* Magnesium | * [[Magnesium]] | ||
* Glucose | * [[Glucose]] | ||
* Arterial blood gases | * [[Arterial blood gases]] | ||
* Aldosterone level | * [[Aldosterone]] level | ||
* Renin levels | * [[Renin]] levels | ||
* Urinary sodium | * Urinary sodium | ||
* Urine potassium | * Urine potassium | ||
** Levels <25 meq/ | ** Levels <25 meq/day (or <15 meq/L on urine spot) rule out a renal cause of hypokalemia and suggest extrarenal potassium loss or transcellular shift | ||
** Higher potassium excretion suggest renal losses. | ** Higher potassium excretion suggest renal losses. | ||
* Transtubular potassium gradient (TTKG) | * Transtubular potassium gradient (TTKG) | ||
** TTKG= (Urine K x Plasma osmolarity)/(Plasma K x Urine osmolarity) | ** TTKG= (Urine K x Plasma osmolarity)/(Plasma K x Urine osmolarity) | ||
** A TTKG less than 2-3 indicates renal potassium conservation in a hypokalemic patient | ** A TTKG less than 2-3 indicates renal potassium conservation in a hypokalemic patient | ||
** A urine osmolality less than plasma osmolality or urine sodium <20 mEq/L, the formula is not applicable | ** A [[urine osmolality]] less than [[plasma osmolality]] or urine sodium <20 mEq/L, the formula is not applicable | ||
* Urine chloride | * Urine chloride | ||
** <25 meq/L: vomiting or remote diuretic use | ** <25 meq/L: vomiting or remote diuretic use | ||
** >40 meq/L: | ** >40 meq/L: [[diuretic]]s, Bartter's, Gitelman's and [[mineralocorticoid]] excess | ||
==References== | ==References== |
Revision as of 14:25, 27 February 2013
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Assistant Editor(s)-In-Chief: Jack Khouri
Overview
Many labs can be helpful. The transtubular potasium gradient (TTKG), urine potassium and urine chloride levels can help define the etiology of hypokalemia.
Laboratory Findings
- Complete blood count (CBC)
- Blood urea nitrogen (BUN)/creatinine
- Calcium
- Magnesium
- Glucose
- Arterial blood gases
- Aldosterone level
- Renin levels
- Urinary sodium
- Urine potassium
- Levels <25 meq/day (or <15 meq/L on urine spot) rule out a renal cause of hypokalemia and suggest extrarenal potassium loss or transcellular shift
- Higher potassium excretion suggest renal losses.
- Transtubular potassium gradient (TTKG)
- TTKG= (Urine K x Plasma osmolarity)/(Plasma K x Urine osmolarity)
- A TTKG less than 2-3 indicates renal potassium conservation in a hypokalemic patient
- A urine osmolality less than plasma osmolality or urine sodium <20 mEq/L, the formula is not applicable
- Urine chloride
- <25 meq/L: vomiting or remote diuretic use
- >40 meq/L: diuretics, Bartter's, Gitelman's and mineralocorticoid excess